1. Field of the Invention
The present invention relates to an image sensor module, a method of manufacturing the same, and a camera module using the same, in which the size of the camera module is reduced to thereby strengthen competitiveness in cost and product.
2. Description of the Related Art
In general, a ceramic package is packaged by a ceramic material so as to protect a chip such as an IC chip from the outside, and has multiple pins formed outside so as to be fixed to a printed circuit board (PCB). The ceramic package constructed in such a manner serves as a path for emitting heat, protects an IC mounted therein from the external environment, and is sealed so as to endure an external impact. The reason why ceramic is used as a package is that the ceramic has higher heat conductivity than other materials, is not easily deformed by heat, has a dielectric constant favorable for transmitting signals and low dielectric loss as an insulating body, and is chemically stable and excellent in combination with metallic material of wiring pattern.
As a method of packaging an image sensor for camera, there are provided a flip chip chip-on-film (COF) method, a wire bonding chip-on-board (COB) method, a chip scale package (CSP) an the like, among which the COF and COB methods are widely used.
The COB method is a similar process to that of an existing semiconductor production line and has higher productivity than other packaging methods. However, since wire should be used for the connection with a PCB, the size of a module increases and an additional process is needed. Therefore, a new packaging technique is required to reduce the size of chip, to enhance heat emission and electrical performance, and to improve reliability. Accordingly, a COF method has emerged, based on bumps having an external bonding projection.
In the COF method, a space for attaching wire is not needed. Therefore, the area of a package and the height of a lens barrel can be reduced. Further, since a thin film or flexible printed circuit board (FPCB) is used, a reliable package which endures an external impact can be manufactured and the process thereof is relatively simplified. Moreover, the COF method satisfies such a tendency that signals are processed at high speed, high density is required, and multiple pins are needed.
The COF method is implemented as chip size wafer-scale packaging. However, the process cost thereof is expensive, and the correspondence to the due date is unstable. Therefore, the method has a limit as a method for image sensor.
Further, in a module using a mega-quality sensor to which various functions are added, the miniaturization of module, which has been a merit of the COF method, is not realized any more, because of the one-story structure. The module cannot but be designed to have a larger size than in the COB method.
Currently, a double-sided flexible printed circuit board (FPCB) is used so that a module can be designed to have a similar size to that in the COB method, which does not satisfy the miniaturization of module which is a merit of the COF method. Therefore, since the COB method tends to be frequently used, the design and process technique for implementing the miniaturization of module are required.
Then, the conventional image sensor module using the COF method will be described with reference to accompanying drawings, and the problems thereof will be examined.
FIG. 1 is a cross-sectional view illustrating a camera module including the image sensor module according to the related art, and FIG. 2 is a plan view illustrating the image sensor module according to the related art. In the drawings, it is shown that multilayer ceramic capacitors 20 and the image sensor 18 are attached on one side of a flexible printed circuit board (FPCB) 16.
As shown in FIG. 1, the camera module including the conventional image sensor includes a housing 1 having a lens 12 provided in an opening thereof, an IR cut filter 14 which is installed inside the opening of the housing 10 provided with the lens 12, and an image sensor module which is installed inside the housing 10 and is composed of the FPCB 16 having multiple multilayer ceramic capacitors 20 and the image sensor 18 formed on one side thereof. In the image sensor module shown in FIG. 2, a window 16a for transmitting an image signal to the image sensor 18 installed in the opposite side is formed in the FPCB 16, the image signal being transmitted through the lens 12 and the IR cut filter 14. At this time, the image sensor 18 serves to process a received image signal, and the IR cut filter 14 serves to cut infrared rays incident from the outside. Further, the multilayer ceramic capacitors 20 serve to remove screen noise generated in the camera module.
In the conventional image sensor module having such a construction, however, the image sensor 18 is attached on the same surface as the surface of the FPCB 16 on which the multilayer ceramic capacitors 20 are installed. Therefore, the overall size of the image sensor module increases, which is occupied on the FPCB 16.
In the conventional image sensor module, if the camera module is limited to a constant size by the request of a user, an active or passive element including the multilayer ceramic capacitor 20 should be inevitably removed from the image sensor module in order to design a product within the limited size of the camera module. At this time, if the multilayer ceramic capacitor 20 is removed from the image sensor module, screen noise occurs. However, such problems are inevitable in order to reduce the overall size of the camera module including the housing.
Furthermore, when the multilayer ceramic capacitors 20 are installed in the conventional image sensor module in order to remove screen noise, there is a limit in reducing the size of the camera module, because the multilayer ceramic capacitor 20 and the image sensor 18 should be attached on one side of the FPCB 16.